Albizia is a genus of about 150 species of mostly fast-growing subtropical and tropical trees and shrubs in the subfamily Mimosoideae of the legume family, Fabaceae. The genus is pantropical, occurring in Asia, Africa, Madagascar, Central, South, and southern North America and Australia, but mostly in the Old World tropics. Some species are considered weedy.
Albizia amara flowers in Shamirpet, India. They are commonly called silk trees or sirises. Peculiarly, the obsolete form of spelling the generic name – with double ‘z’ – has stuck, so that another commonly used term is albizzias (though the form albizias is also found, particularly in species that are not widely known under a common name). The generic name refers to the Italian nobleman Filippo degli Albizzi, who in the mid-18th century introduced siris to Europe.
These are usually small trees or shrubs with a short lifespan – though the famous Samán del Guère near Maracay in Venezuela is a huge Albizia saman specimen and several hundred years old. The leaves are pinnately or bipinnately compound. Their small flowers are in bundles, with showy stamens much longer than the petals. Confusingly, some species are given the name “mimosa” which correctly belongs to species in the related genus Mimosa. Unlike those of Mimosa, Albizia flowers have much more than 10 stamens. Albizia can also be told apart from another large related genus, Acacia, since its flowers have their stamens joined at the base whereas in Acacia stamens are free (separated).
Persian Silk Tree or Pink Siris (Albizia julibrissin) extends well north into temperate regions in East Asia and is by far the cold-hardiest species. It tolerates temperatures down to about −30 °C (−22.0 °F), provided it gets adequate summer heat to ripen the shoots. In North America it is commonly grown as an ornamental tree, but has become naturalized in several US states, and is regarded as an invasive species. Albizia species are used as food plants by the larvae of some moths of the genus Endoclita inclulding E. damor, E. malabaricus and E. sericeus.
Albizia saman is a species of flowering tree in the pea family, Fabaceae, that is native to the Neotropics. Its range extends from Mexico south to Peru and Brazil, but it has been widely introduced to South and Southeast Asia, as well as the Pacific Islands, including Hawaii. Common names include Saman, Rain Tree and Monkey Pod (see also below). It is often placed in the genus Samanea, which by yet other authors is subsumed in Albizia entirely. Saman is a wide-canopied tree with a large symmetrical crown. It usually reaches a height of 25 m (82 ft) and a diameter of 40 m (130 ft). The leaves fold in rainy weather and in the evening, hence the name Rain Tree and 5 o’clock Tree (Pukul Lima) in Malay. Several lineages of this tree are available e.g. with reddish pink and creamish golden colored flowers.
During his 1799-1804 travels in the Americas, Alexander von Humboldt encountered a giant Saman tree near Maracay (Venezuela). He measured the circumference of the parasol-shaped crown at 576 ft (about 180.8 m), its diameter at around 190 ft (about 59.6 m), on a trunk at 9 ft (about 2.8 m) in diameter and reaching just 60 ft (nearly 19 m) in height. Humboldt mentioned that the tree was reported to have changed little since the Spanish colonization of Venezuela; he estimated the Saman to be as old as the famous Canary Islands Dragon Tree (Dracaena draco) of Icod de los Vinos on Tenerife.
The tree, called Samán del Guère (transcribed Zamang del Guayre by von Humboldt) still stands today and is a Venezuelan national treasure. Just like the dragon tree on Tenerife, the age of the Saman in Venezuela is rather indeterminate. As von Humboldt’s report makes clear, according to local tradition it would be older than 500 years today, which is rather outstanding by the genus’ standards. It is certain however than the tree is quite more than 200 years old today. But it is one exceptional individual; even the well-learned von Humboldt could not believe it was actually the same species as the Saman trees he knew from the greenhouses at Schönbrunn Castle.